Added a note to the serialization section regarding desugared names #21263

* Updated note with changes from PR

* Updated note with changes from PR

akka-docs/rst/java/serialization.rst

@@ -35,6 +35,14 @@ one of which all other candidates are superclasses. If this condition cannot be
 met, because e.g. ``java.io.Serializable`` and ``MyOwnSerializable`` both apply
 and neither is a subtype of the other, a warning will be issued.
 
+.. note::
+
+  If you are using Scala for your message protocol and your messages are contained
+  inside of a Scala object, then in order to reference those messages, you will need
+  use the fully qualified Java class name. For a message named ``Message`` contained inside
+  the Scala object named ``Wrapper`` you would need to reference it as
+  ``Wrapper$Message`` instead of ``Wrapper.Message``.
+
 Akka provides serializers for :class:`java.io.Serializable` and `protobuf
 <http://code.google.com/p/protobuf/>`_
 :class:`com.google.protobuf.GeneratedMessage` by default (the latter only if

akka-docs/rst/scala/serialization.rst

@@ -35,6 +35,13 @@ one of which all other candidates are superclasses. If this condition cannot be
 met, because e.g. ``java.io.Serializable`` and ``MyOwnSerializable`` both apply
 and neither is a subtype of the other, a warning will be issued
 
+.. note::
+
+  If your messages are contained inside of a Scala object, then in order to
+  reference those messages, you will need use the fully qualified Java class name. For a message
+  named ``Message`` contained inside the object named ``Wrapper``
+  you would need to reference it as ``Wrapper$Message`` instead of ``Wrapper.Message``.
+
 Akka provides serializers for :class:`java.io.Serializable` and `protobuf
 <http://code.google.com/p/protobuf/>`_
 :class:`com.google.protobuf.GeneratedMessage` by default (the latter only if